Angiography (or arteriography) is an imaging process used to visualize cardiac chamber size and segmental wall mobility and coronary size, morphology, flow, anatomy and arterial luminal size by displaying static and dynamic image silhouettes. This provides the ability to assess cardiac and coronary arterial function and calculate estimations of cardiac chamber volumes (Ventricular and Atrial), which facilitates diagnosis of cardiac disease. In known systems, electrophysiological signals (such as ECG signals and intra-cardiac electrograms in electrophysiology procedures) and time domain parameters of ECG waveforms are typically utilized as synchronizing and gating signals to trigger imaging by an imaging system. A QRS synchronizing pulse is used to initiate image acquisition in X-ray imaging, for example, to obtain an optimum quality image at a desired time. However, an electrophysiological signal, such as an R wave may not be the best signal for cardiac function diagnosis and may lack precision for synchronizing image acquisition for diagnosis of specific cardiac function or tissue pathologies. For example, an electro-cardiac spike (such as a QRS complex) may not provide an accurate time gating signal for maximum volume image capture and calculation of cardiac chambers, such as a left ventricle for systolic and diastolic volume. Additionally, known systems used in image diagnosis, characterization and evaluation are subjective and need extensive medical expertise and clinical experience for accurate interpretation and appropriate cardiac rhythm management.
Stable, accurate and high quality image scanning and capture are desirable for physicians to be able analyze and diagnose cardiac functions and tissue status, such as cardiac diseases and pathology evaluation and characterization. Known imaging systems, such as X-ray and ultrasound imaging systems, usually capture images in an unsynchronized manner or are time parameter based. Surface ECG gating (mainly QRS complex/R wave gating) and respiration signals are also employed to synchronize an image scanning sequence and timing for image acquisition and capture. The surface and respiration gating and synchronization facilitate reduction of patient artifacts and bio-noise (heart beating, respiration and related patient movements). However, in known clinical procedures and applications, there is a lack of an efficient, effective method for cardiac function based gating and synchronization for image acquisition and diagnosis.
In assessing valve disease and heart failure patients, for example, imaging systems for use in cardiac volume and cardiac output analysis, provide flow, volume and regurgitant volumes valuable in diagnosis. Known systems lack accurate gating to measure maximum volume of a chamber and may also use retrospective image evaluation to extract an image of maximum volume, for a left ventricle chamber, for example. However, an image database used for retrospective analysis may not contain an image of maximum volume and size. Known medical imaging systems usually use gating for elimination and reduction of patient noise and artifacts (such as from respiration and heart beating) but lack comprehensive function gating and imaging synchronization capability. Tuning image acquisition rate and the use of high speed scanning in known systems may cause inefficient usage of a scanning system which may reduce the life of the image system, such as an X-ray machine. In order to diagnose patient cardiac functions, a physician may have to use frequent scanning and image acquisition. This may cause radiation over-dose and inefficient usage of an image acquisition system. Also accurate imaging of maximum volume cardiac chambers is desirable to identify long term hypertension effects (early effects may cause 3-5% size expansion of the heart chambers). A system according to invention principles addresses the identified needs and deficiencies and associated problems.